Cycloolefin monomers which contain a norbornene group are known to polymerize by ring-opening polymerization and addition polymerization. Polymers obtained by a ring-opening polymerization of cycloolefins that contain the norbornene group are well known. For example, U.S. Pat. Nos. 4,136,249; 4,178,424; 4,136,247 and 4,136,248, assigned to the same assignee of the present invention, describe such polymers, and each is incorporated herein by reference for the description of polymers therein.
Ring-opening polymerization of cycloolefins yields unsaturated linear polymers which are of particular interest in that they are known to be reactive (sulfur-vulcanizable) and they are known to exhibit attractive property profiles for many polymer applications, such as, for example, as automotive parts, particularly decorative trim.
Dicyclopentadiene and cyclopentene are common cycloolefin monomers used to prepare ring-opening polymerized polymers in that these cycloolefin monomers are readily available as by-products in ethylene production. Recent U.S. Patents directed to cyclopentene and dicyclopentadiene polymers include U.S. Pat. Nos. 3,778,420; 3,781,257; 3,790,545; 3,853,830 and 4,002,815. Other well known cycloolefin monomers include bicyclic norbornene (bicyclo[2.2.1]-hept-2-ene) and substituted bicyclic norbornenes, which are produced by Diels-Alder reaction of cyclopentadiene with selected olefins.
Dicyclopentadiene monomers produce ring-opened polymerized polymers with excellent glass transition temperatures of about 160.degree. C. However, there is a continuing effort to obtain ring-opened polymerized polymers with higher values for glass transition temperature to expand the use of such polymers to applications requiring higher heat resistance. Methods and compositions which provide ring-opened polymerized polymers with higher Tg values than dicyclopentadiene polymers are known. Typically, cycloolefin monomers having a greater number of ring structures combined with a molecular weight greater than dicyclopentadiene provide polymers and copolymers with higher Tg values when substituting for dicyclopentadiene. For example, tetracyclododecene and substituted tetracyclododecenes are well known cycloolefin monomers made by Diels-Alder reaction of cyclopentadiene with bicyclic norbornene or the appropriate substituted bicyclic norbornene. These tetracyclododecenes have higher molecular weights and more ring structures than dicyclopentadiene. Tetracyclododecene homopolymers have higher Tg values than homopolymers of dicyclopentadiene and where used in copolymers with bicyclic norbornenes, they provide a greater enhancement of Tg values than dicyclopentadiene.
However, cycloolefin monomers having a higher molecular weight and a greater number of ring structures than dicyclopentadiene are not easily obtained. Such "high molecular weight" cycloolefins must be synthesized in a process separate from the polymerization procedure, typically from dicyclopentadiene and/or cyclopentadiene starting materials. The need for a separate synthesis is disadvantageous in that such a process adds significantly to the cost of the final product and may introduce undesirable impurities to the polymerization process. Impurities often reduce the degree of conversion of the cycloolefin monomers in forming the ring-opened polymerized product and high levels of unconverted monomer within the final polymerized product can render the material unsuitable for molding rigid articles. To maintain high levels of conversion, the synthesized "high molecular weight" cycloolefin may need to be purified, which also adds to the cost of the final product.
It is desirable to obtain a more convenient source of cycloolefin monomers with higher molecular weights and more ring structures than dicyclopentadiene. In addition, it is desirable to provide a convenient method for utilizing these "high molecular weight" cycloolefin monomers within a polymerization scheme. It would be advantageous for such a method to be sufficiently flexible so as to provide "high molecular weight" cycloolefin monomers suitable for use in ring-opening polymerization reactions and addition polymerization reactions utilizing either solution or bulk polymerization techniques.